Several multi-radio systems-on-chip (SoCs) include multiple on-chip radio frequency (RF) circuits that coexist and operate on a single silicon die. Such SoCs include digital circuit as well as analog circuits integrated on the same silicon die. For example, a SoC is designed to accommodate wireless local area network (WLAN) systems, short range wireless communication systems, and frequency modulation (FM) radio systems thereon.
The RF circuits co-existing on the SoC causes interference issues in efficient operation of the SoCs. For example, the digital circuits in the SoC significantly contribute to the interference when the harmonics of the frequencies of a digital clock associated with the digital circuits fall in a band of interest of RF circuits. As such, the RF circuits will not function as expected. In various exemplary scenarios, such harmonics of the frequencies of the digital clock signals are referred to as spurs or spurious signal.
If the spurs caused by digital activity occur in the band of interest of RF circuits on the SoC, they cause degradation in the performance of RF circuits. For example, the spurs change the noise floor, thereby impacting the detection of channel presence. When the location of the interfering frequency band is closely related to the harmonics of the frequencies of the digital clock, choosing the frequency of the digital clock becomes difficult.